In an internal combustion engine, if valve overlap occurs when the pressure inside an intake port is higher than the pressure inside an exhaust port, air is blown from the intake passage through the cylinder to the exhaust passage in what is known as “scavenging”. In an internal combustion engine provided with a supercharger such as a turbocharger, scavenging is intentionally caused if the amount of intake air is insufficient for the requested torque. By causing scavenging, the amount of exhaust gas increases and the speed of the turbine of the supercharger is raised. As a result, the pressure of the intake air is raised and the amount of intake air is increased.
Known in the past has been an internal combustion engine configured to provide an air-fuel ratio sensor in an exhaust passage of the internal combustion engine and control the amount of fuel fed to a combustion chamber of the internal combustion engine so that the output of this air-fuel ratio sensor matches a target air-fuel ratio (for example stoichiometric air-fuel ratio (14.6)) (for example, PLT 1). In such control, during scavenging, the amount of fuel fed to a combustion chamber is controlled so that the average air-fuel ratio of the exhaust gas including the air blown from the intake passage through the cylinder to the exhaust passage becomes the target air-fuel ratio.